US Secretary of Defense Lloyd Austin arrived in Israel on Sunday on the first visit by a senior representative of the Biden administration, whose stance on Iran has worried Prime Minister Benjamin Netanyahu's government.
Austin was due to meet Netanyahu and Israeli Defence Minister Benny Gantz during the two-day visit, which officials said would include discussions of US arms supplies to Israel, Reuters said.
Washington has sought to reassure Israel on regional security issues while restarting talks - so far indirect and inconclusive - about a US return to the 2015 nuclear deal between major powers and Iran that the previous Trump administration quit.
Israel has long been critical of the deal that it sees as putting a temporary cap on Iranian nuclear capabilities that would pave the way to Tehran producing bombs in the long run. It has said it would not be bound by the diplomacy.
Israel and Iran have in recent weeks reported sabotage to their ships at sea. Syria has accused Israel of air strikes on its territory. Israel says it is trying to stem a build-up of Iranian forces within next-door Syria.
On Sunday, Iran's Press TV said an electricity problem had caused an incident at the Natanz underground uranium enrichment site, without casualties or pollution. Tehran says its nuclear programme is for peaceful purposes only.
Israel, which lists cyber-sabotage in its arsenal, had no immediate comment on the Natanz incident.
Austin's visit comes just days after Washington said it had offered "very serious" ideas on reviving the hobbled agreement that is staunchly opposed by Israel.
Israel under hawkish Prime Minister Netanyahu has been a fierce critic of the Iran nuclear deal, dating back to when it was being negotiated during Barack Obama's administration.
Netanyahu applauded when Trump withdrew from the deal and imposed sanctions on Tehran, which responded by stepping back from several of its commitments under the deal.
In the latest breach of its undertakings in the troubled agreement, Tehran announced on Saturday that it had started up advanced uranium enrichment centrifuges.
President Hassan Rouhani inaugurated a cascade of 164 IR-6 centrifuges for producing enriched uranium, as well as two test cascades -- of 30 IR-5 and 30 IR-6S devices respectively -- at Iran's Natanz uranium enrichment plant, in a ceremony broadcast by state television.
In an address marking the eve of Holocaust Remembrance Day, Netanyahu said on Wednesday that Israel would not be bound to a nuclear deal that would enable the Islamic republic to develop nuclear weapons.
"An agreement with Iran that would pave the way to nuclear weapons -- weapons that threaten our extinction -- would not compel us in any way," said the veteran right-wing premier, said as quoted by AFP.